Process for crystallizing borax from solutions



Patented Feb. .19, 1935 moms roa CRYSTAIJJIZ-I NGaBORAXI FROM SOLUTIONSr (Alfred Newman, Long Beach," Calif; assignor' 'to Pacific Coast BoraxCompany, a corporation-of Nevada J "No Drawing. Application lulyl30,1932, I f

. d :lSerialNo. 627,133 y 6 Claims. (eras- 59) :Thisinvention has to doina general way with the art of crystallizatiomiand is more particu-jlarly related to the production of borax crystals from agitated aqueoussolutions of borax. v

--Itis well known to those familiar with the art, that if any aqueoussolution of borax, which, by way of illustration, may contain 20 to 30%crystal vborax in solution, is placed in a tank and is agitated in anysuitable manner and rapidly cooled by any suitable means,'suchas-contact with ,pipe coils through which a refrigerant, coolerthan the borax liquid, is flowing, or by. rapidly evaporating the waterfrom the borax solution in aso-called vacuum cooler, the borax crystalswhich precipitate from the solution are chiefly aggregates of smallcrystals, the individual particles having no definite form or shape.vFor convenience-I define such crystals as type one. [Beingof irregularshape the crystals readily cohere-and upon packing the mass-of crystalsoften becomes (compact {and hard and thus as commonly defined becomescaked. Although borax crystals formed-in this'way arej -adapted for manyuses it has been found advantageous for some purposes to formacrystalline borax, the

individual ,3 particles of which are of definite crystalform'withdistinct, crystal faces characteristicofborax or NazBiOmlOHzO. Forconvenience Idefine such crystals as type two. I Such crystals, onaccount of their definite crystal form and distinct'crystal faces, donot cohere or cake tothe same degree as crystals of type one.

The trade having cometo demand larger crystals it'has beenfounddesirable to produce by rapid cooling crystalline borax" of a sizelarger than type one. Ithas been foundthat the typeone-crystals hithertoproduced-by rapid cooling have approximately the following meshz-,Tyler' Cumulative Tyler Cumulativemesh ,7 percent 'mesh percent 14 0.30v 149.27 20 3.53 86179 28 30i83 -l50 I 91.52 35 57.15 200 94.82; 48 70.40 200 '100. 00

By the process herein described it hasbeen found possible to producecrystals of type two having the following mesh:

yl r T ler' Cumulative y Cumul t standar a We mesh percent gh pfrcentThe'productionof boraxgcrystals of type two has hitherto been.caccom'plished, first by very slow. cooling .of the ,borax solution,and second,

by adding a small amountof soap, fatty acid, or

other emulsion colloidflof similar nature tothe hotboraxsolution.eitherprior to. or during the step of rapid cooling andagitation. V i Thejprocess of slow cooling obviously has markeddisadvantages in the commercial process,

since the time, from 6 to 7 days and equipment required for theproduction ofl-a given amount of this typeiof borax is muchgreater thanthat which is necessary in a process ,that. canbe car- The use of soap,fattywa'cid, or other emulsion colloids v often results. in:aquantityrof the agent beingentrained 'or entangled in the boraxcrystal, This quantity is suflicient to yield adiscolored-glass when the'borax is fused, .and'when the borax is placed in warm water and themixture ried out by rapid cooling,:say frame to. 5 hours. a

shaken the quantity is sufficient to produce a foam onlather similar;tothat'whensoap isadded to warm; water. I l It,-is a primary :object'ofmy invention to.-produceborax crystals of -typetwoaand at thesame timevto avoid the. undesirable results noted above I- have discoveredthatthegobj ectcontemplated by my invention can be attainedsimply by seedinga hot }b orax solution with a suitable quantity of borax crystals formedby the process of-slow cooling anotherhot .borax solution. L It ispreferable that the borax'usedfas] seed crystals be deposited fromsolution without agitation; Byslowcoohng. Ikrefertothe type of processfirst enumerated above in which the hot boraxsolution is -cooled merelyby radiationtothe atmosphereover .a

substantial periodof time. Aspointed out above,- the: borax crystals.formed by -such a cooling process areof well defined crystallineformand shape and I have'discovered that they have the peculiar property,whenadded as seed" crystals to another hot borax solution, ofcausing-the crystalsiformed from the latter-solution'to also be ofwellidefined'crystal formsand shape with distinct crystalfaces. Thisproperty; seems to be -peculiar tothecrystalsformedbythe slow coolingprocess,

and the. '15 act is of particular ,value; in'that'the seeded solutioncan be rapidly,;cooled;-;and;gagitated during crystallization without inany way interfering with the formation of the individual crystals. I

The following example is given for the purpose of more clearlyillustrating the process contemplated bymy invention. First, fourthousand gallons, of hot aqueous solution of borax containing, saythirty, per cent crystal borax, placed in a tank and allowed to cool byradiation of heat into the atmosphere for a period of six days. Thistime may be greater or less within certain limits without in any wayaffecting the results of the process. The crystal borax'thus formed isseparated from the liquor and the crystals are crushed to a suitablesize for use as seeds. I have found that the best results are obtainedif the seed crystals are larger than what will pass a sixty-five meshTyler standard screen, or a screen having an opening of .0082 inch.

After a suitable quantity of these seed crystals has been prepared, inthe manner described.

above, another suitable quantity, say four thousand gallons of hotaqueous solution of borax of approximately 185 F., containing, saytwentyeight per cent crystal borax, is placed in a tank, agitated, andrapidly cooled in any suitable manner until a temperature ofsubstantially 135 F.-

' limits by controlling the time over which the agitation and coolingtakesplace. 7 It has been found that proceeding in the above describedmanner crystals of the aforementioned characteristics are produced. 7

I have found that the mother liquor can be removed much more easily fromcrystals formed in the process contemplated by this invention than fromthe aggregation type of crystals 'ordinarily produced by rapid cooling ahot borax solution. 3 As a further advantage of producing larger sizecrystals, a given weight of the material when packed for shipment,occupies a volume of approximately eighty percent the volume occupied bythe same weight of borax of the aggregation crystal type. My process,therefore, has the advantage of reducing the cost of production, (as

compared with borax produced by the slow cooling;process) reducing thecost of packing T and shipping, (as compared'with the aggregate type ofcrystal) and supplying to the trade crystals ofborax which do notreadily cake, and of a size suitably larger;

It will be noted from the foregoingdescription that 'Ihave used fourthousand gallons as the quantity of solution from-which the seedcrystals are prepared and have also, referred-to four thousand gallons"asthe quantity of solution which is rapidly cooled. It is to beunderstood of course that the quantity of seed 'ory'stals' added to thesecond solution is a comparatively. small percentage of the totalquantity of seed crystals produced during the slow cooling step. It isto' be understoodthat the term concen-' tratedsolution as used hereinhas reference to a borax solution'of a temperature'andtconcentrationsuitable for seeding without dissolving the seed crystals. 1

It is to be understood that, while I have herein referred to onepreferred method of practicing this process, the invention is notlimited by the precise terms of the foregoing description but includeswithin its scope whatever changes fairly come within the spirit of theappended claims. I claim as my invention:

1. A process of crystallizing borax of definite crystal form and withdistinct crystal faces from aqueous solution which comprises slowcooling a hot aqueous solution of borax to crystallize borax therefrom;pulverizing and screening borax crystals thus obtained to a finenesssuch that it will be retained on a screen of .00082 inch opening;seeding a second hot concentrated solution with the pulverized crystals;and rapidly cooling the second solution.

2. A process of crystallizing borax of definite crystal form and withdistinct crystal faces from aqueous solution which comprises slowcooling a hot aqueous solution of borax to crystallize borax therefrom;pulverizing and screening the borax crystals thus obtained to' afineness such that it will be retained on a screen of .0082 inchopening; seeding a second hot concentrated solutionwith the pulverizedcrystals; and rapidly cooling the'second solution with agitation.

3. A process of crystalliz'ing borax of definite form with distinctcrysta'lfaces from a concentrated'a'queous solution which comprisesrapidly cooling said solution and seeding the same with borax crystalsobtained by slow cooling another borax solution, said seed crystalsbeing of a size such that they will be retained on a screen having anopening 'of .0082 inch. 7

4. A processof crystallizing' borax of definite crystal formwithdis'tinct "crystal faces from a concentrated aqueous solution whichcomprises rapidly cooling said solution and seeding the same with boraxcrystals obtained by slow cooling another borax solution, said seedcrystals being of a size-such that they will produce particles of welldefined crystalline form and shape.

5'. A process of crystallizing borax of definite form with distinctcrystal faces from a concentrated aqueous solution which comprisesrapidly cooling and agitating said solution and seeding the same withboraxcrystals obtainedby slow cooling another borax solution, said seedcrystals being of a size such thatthey will be retained on a'screenhaving an opening of .0982 inch.

'6. A process of crystallizing borax of definite crystal'form withdistinct crystal faces from a concentrated aqueous solution whichcomprises rapidly cooling and agaitating said solution and seeding thesame with borax crystals obtained by slow cooling another boraxsolution, said seed crystals being of a size such that they will produceparticles of well defined crystalline form and shape. I

' ALFRED NEWMAN.

